Methods for producing nucleoside derivatives and intermediates therefor

ABSTRACT

Novel intermediates of nucleoside derivatives, of which the 6-position of the nucleic acid base moiety is substituted with a halogen atom, are produced. Using those novel intermediates, even substrates, of which the 3′-position of the saccharide moiety is deoxylated, can be substituted at the 2′-position at an extremely high yield. Specifically, by subjecting a 3′-deoxy derivative of inosine to 6-halogenation to give a 6-halide of the derivative, and then subjecting it to 2′-deoxylation/substitution with a fluorine atom or the like, followed by further subjecting it to substitution with an amino group, a hydroxyl group or any other intended substituent at the 6-positioned halogen atom, nucleoside derivatives are produced at a high yield. Methods for producing nucleoside derivatives including 9-(2,3-dideoxy-2-fluoro-β-D-threo-pentofuranosyl)adenine (FddA) and their related compounds, in a simplified manner, at a high yield and at low costs, and especially Economical methods for substituting substrates, of which the 3′-position of the saccharide moiety is deoxylated, at the 2′-position to produce those nucleoside derivatives on an industrial scale are also provided.

This application is a Continuation of U.S. application, Ser. No.09/267,789, filed Mar. 15, 1999, now allowed, now U.S. Pat. No.6,090,937.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a novel method for producing nucleosidederivatives, more precisely to a novel method for producing nucleosidederivatives including9-(2,3-dideoxy-2-fluoro-β-D-threo-pentofuranosyl)adenine (hereinafterreferred to as “FddA”) and its related compounds which are useful asanti-viral agents, to novel intermediates in the method, and to a novelmethod for producing the intermediates.

2. Description of the Related Art

It is reported that9-(2,3-dideoxy-2-fluoro-β-D-threo-pentofuranosyl)adenine (FddA) has astrong anti-viral activity against human immunodeficiency virus (HIV)and is greatly effective for treatment of acquired immune deficiencysyndrome (AIDS) (see V. E. Marquetz, et al., Biochem. Pharmacol., (36)page 2719, 1987; P. Herdewijn, et al., J. Med. Chem., (30), page 2131,1987), and many clinical tests using it for the treatment of AIDS andAIDS-related complications (ARC) are being made at present. Recently, inaddition, reported are FddA derivatives as modified at the nucleic acidbase site to improve their potency (see C. K. Chu, et al., J.Med. Chem.,(37), page 821, 1994; J. S. Driscoll, et al., J. Med. Chem., (39), page1619, 1996; C. K. Chu, et al., J. Med. Chem., (39), page 4676, 1996).

The most direct method for producing FddA and its related compoundscomprises substituting a substrate, of which the 3′-position in thesaccharide moiety is deoxylated, at its 2′-position (see P. Herdewijn,et al., J. Med. Chem., (30), page 2131, 1987; V. E. Marquez, et al., J.Med. Chem., (33), page 978, 1990; H. Shiragami, et al., Nucleosides &Nucleotides, (11), page 391, 1992). However, the yield in theconventional methods is extremely low or is not higher than 10% and thereagent, diethylaminosulfer trifuluoride (DAST), is not available inindustrial amount, and therefore the methods could not be used forindustrial production of FddA and its related compounds.

1. Problems to be Solved by the Invention

In the course of the completion to the present invention, the above andfollowing problems in the related art have been also found by thepresent inventors.

Given the situation as above, it is desired to develop an inexpensivemethod for producing nucleoside derivatives including9-(2,3-dideoxy-2-fluoro-β-D-threo-pentofuranosyl)adenine (FddA) and itsrelated compounds, in a simplified manner and at a high yield, inparticular, an economical and industrial method for producing thosenucleoside derivatives that comprises substituting a substrate, of whichthe 3′-position of the saccharide moiety is deoxylated, at its2′-position at a high yield. Accordingly, the subject matter in the artis to provide such an excellent production method.

The object of the present invention is to develop an advantageous methodfor producing the nucleoside derivatives noted above, especially thosehaving anti-viral activity, and to provide intermediates in the methodand also a simple method for producing the intermediates.

SUMMARY OF THE INVENTION

We, the present inventors have assiduously studied in order to solve theproblems noted above, and, as a result, have found, in a process forproducing nucleoside derivatives including9-(2,3-dideoxy-2-fluoro-β-D-threo-pentofuranosyl)adenine (FddA) and itsrelated compounds, by subjecting a 3′-deoxy derivative of adenine to2′-deoxylation/substitution with a flurine atom or the like (see P.herdewijn, et al., J. Med. Chem., (30), page 2131, 1987; V. E. Marquez,et al., J. Med. Chem., (33), page 978, 1990; H. Shiragami, et al.,Nucleosides & Nucleotides, (11), page 391, 1992 ), the yield thereof isextremely low mainly due to a rearrangement of adenine base.

It is reported that, by subjecting a derivative of adenine, of which the3′-position is not deoxylated, to 2′-deoxylation/substitution with afluorine atom or the like, the same kind of rearrangement has occurredas side reaction and lowered the yield (see K. A. Watanabe, et al., J.Org. Chem., (57), page 553, 1992 ). Furthermore, it is reported that, bychlorination at the 6-position of the nucleic acid, this kind ofrearrangement can be suppressed (see T. Maruyama, et al., Chem. Pharm.Bull., (44), page 2331, 1996). However, it is not known the case of3′-deoxy derivatives.

Therefore, we, the present inventors have produced novel intermediatesof a general formula (1) mentioned below, which are derivatives asdeoxylated at the 3′-position and substituted by a halogen atom at the6-position of the nucleic acid. Using those novel intermediates, we havefound that even substrates, of which the 3′-position of the nucleic acidis deoxylated, can suppress the troblesome rearrangement completely andcan be substituted at the 2′-position at an extremely high yield. On thebasis of these findings, we have completed the present invention.

Specifically, by subjecting a 3′-deoxy derivative of inosine to6-halogenation step for halogenating it at the 6-position thereof togive a 6-halide of the derivative, and then subjecting it to2′-deoxylation/substitution with a fluorine atom or the like, followedby further subjecting it to substitution with an amino group, a hydroxylgroup or any other intended substituent at the 6-positioned halogenatom, we have made it possible to produce the intended nucleosidederivatives.

On the basis of our findings noted above, hereinunder illustrated is oneembodiment of the production route to give nucleoside derivatives, whichcovers all the steps in series as concretely demonstrated in Examples tobe mentioned hereinafter. All those steps and the compounds as producedtherein are usable in the process of producing nucleoside derivatives ofthe present invention. Naturally, the invention encompasses not only allthe steps constituting this production route but also any and everymethod comprising any one of those steps, novel intermediates asproduced in those steps and even the use of those novel intermediates,especially the use thereof for producing various nucleoside derivatives.Production Route:

In those formulae, W represents a halogen atom, X represents a halogenatom, Y represents a substituent of any of a fluorine atom, an azidogroup or a cyano group, Z represents any one of a hydrogen atom, anamino group, a hydroxyl group, an azido group, a substituent of aformula OR⁴, a substituent of a formula SR⁴ and a substituent of aformula NHR⁴, R¹ represents a protective group for the hydroxyl group,SO₂R²represents a sulfonic acid-type leaving group, R³represents aprotective group for the hydroxyl group, and R⁴ represents anoptionally. phenyl-substituted, lower (e.g., C1-5) alkyl group.

Preferably, R² represents a halogen atom, an optionally-substitutedaryl, alkyl or aralkyl group, or an optionally-substituted alkylaminogroup.

Regarding the definitions and the meanings of the compounds of generalformula (1) to (9) as referred to herein, it shall be understood thatthe compounds designated by the same formula number are the same oneseven though they are not individually described herein.

The invention encompasses a novel method for producing the nucleosidederivatives mentioned herein from the novel intermediates (1) and alsofrom various raw compounds, novel intermediates including theintermediates (1) which are for producing the nucleotide derivatives, anovel method for producing those intermediates, and the use of theintermediates. More precisely, the present invention encompasses thefollowing matters.

(i) A method for producing a nucleoside derivative represented by thefollowing general formula (8) or (9), comprising subjecting a 3′-deoxyderivative of inosine, of which a part or all of the two hydroxyl groupsmay or may not be optionally protected, to 6-halogenation step forhalogenating the compound at the 6-position thereof to give a 6-halideof the derivative, and then subjecting it, optionally after protectingits 5′-position, to 2′-deoxylation/Y-substitution reaction step followedby further subjecting it to Z-substitution reaction at its 6-halogenatom:

In the case of optionally protected 5′-position with a protective groupin the derivative, the protective group may be de-protected in thesuitable step, for example, before or after the Z-substitution reactionat its 6-halogen atom.

In such formula, as so mentioned hereinabove, Y represents a substituentof any one of a fluorine atom, an azido group and a cyano group, Zrepresents any one of a hydrogen atom, an amino group, a hydroxyl group,an azido group, a substituent of a formula OR⁴, a substituent of aformula SR⁴ and a substituent of a formula NHR⁴, R¹ represents aprotective group for the hydroxyl group, and R⁴ represents an optionallyphenyl-substituted, lower (e.g., C1-5) alkyl group.

The compound (8) obtained herein may be optionally subjected todeprotection at the 5′-position to convert them into 5′-deprotectedderivative (9), as will be mentioned after.

On the other hand, the obtained compound (8′) mentioned after may beoptionally subjected to substitution with a group Z at its 6-halogenatom to give such derivative (9), as will be also mentioned after.

The nucleoside derivatives, compounds (9) in the present invention haveanti-viral activity, in which Z is preferably a hydrogen atom, an aminogroup, a hydroxyl group, an azido group, a methylamino group, amethyloxy group or the like.

(ii) A method for producing a nucleoside derivative represented by thegeneral formula (8) or (8′) noted above, which comprises subjecting acompound represented by the following general formula (1) to2′-deoxylation/Y-substitution reaction to give a compound represented bythe following general formula (3);

and then subjecting the resulting compound (3) to substitution with agroup Z at its 6-halogen atom to give the compound (8),

or subjecting the compound (3) to deprotection at the 5′-position toconvert the same into 5′-deprotected derivative (8′).

One embodiment of the method comprises a step of processing the compoundof formula (3), especially preferably that in which X is a chlorine atomand Y is a fluorine atom, to thereby substitute the substituent X withan amino group, preferably processing it in a solution of ammonia in analcohol (e.g., methanol, ethanol, propanol, etc.), or a step ofprocessing the compound to thereby substitute the substituent X with ahydroxyl group, preferably processing it in an aqueous solution of analkali hydroxide (e.g., sodium hydroxide, potassium hydroxide, etc.), ora step of processing the compound to thereby substitute the substituentX with a hydrogen atom, preferably processing it with hydrogen in thepresence of a reduction catalyst (e.g., palladium-carbon, Raney nickel,etc.), or a step of processing the compound to thereby substitute thesubstituent X with an azido group, preferably processing it with analkali metal azide (e.g., sodium azide, lithium azide, etc.), to therebyproduceng the nucleoside derivative of formula (8), and optionallycomprises a step of deprotecting the resulting derivative at theprotective group R¹ to obtain a nucleoside derivative represented by thefollowing general formula (9).

Alternatively, the compound firstly (3) may be subjected to such abovedeprotecting step at the protective group R¹ to give the derivative(8′), and then the obtained this derivative (8′) may be subjected tosubstitution with a group Z at its 6-halogen atom to give the compound(9) in the same manner as above.

In those above formulae, as so mentioned hereinabove, X represents ahalogen atom, Y represents a substituent of any one of a fluorine atom,an azido group and a cyano group, z represents any one of a hydrogenatom, an amino group, a hydroxyl group, an azido group, a substituent ofa formula OR⁴, a substituent of a formula SR⁴ and a substituent of aformula NHR⁴, R¹ represents a protective group for the hydroxyl group,and R⁴ represents an optionally phenyl-substituted, lower (e.g., C1-5)alkyl group.

(iii) One embodiment of the method of (ii), wherein the reaction stepincludes a compound of the following formula (2) as the intermediate:

In this formula, as so mentioned hereinabove, X represents a halogenatom, R¹ represents a protective group for the hydroxyl group, and SO₂R²represents a sulfonic acid-type leaving group.

(iv) A method for producing compounds of formula (3) noted above, whichcomprise;

(a) subjecting a compound of formula (1) noted above to2′-deoxylation/Y-substitution reaction step, preferably for removing thehydroxyl group from the compound followed by introducing a substituentY, a fluorine atom, an azido group or a cyano group, thereinto, morepreferably by reacting the compound with an alkylaminosulfur trifluoridereagent or a fluoroalkylamine reagent, or

(b) subjecting a compound of formula (2) noted above to removal of2′-leaving group/Y-substitution reaction step, or that is, processingthe compound to thereby remove its O-sulfonic acid-type leaving grouptherefrom and introduce a substitutent Y, a fluorine atom, an azidogroup or a cyano group, thereinto, preferably by reacting the compoundwith a reagent for attaining the substitution with a fluorine atom, anazido group or a cyano group, for example, reacting it with any one ofazides, cyanides and fluorides, to thereby produce the intended compound(3).

In the meantime, the removal of 2′-leaving group in the presentinvention, the sulfonic acid-type leaving group is removed in the formof the O-sulfonic acid-type leaving group.

In these formulae, as so mentioned hereinabove, X represents a halogenatom, Y represents any one of a fluorine atom, an azido group and acyano group, R¹ represents a protective group for the hydroxyl group,and SO₂R² represents a sulfonic acid-type leaving group. Preferably, R²represents a substituent of any one of a halogen atom, an aryl, alkyland aralkyl group and also an alkylamino group, which may be optionallysubstituted (for example, with a halogen atom, etc.).

(v) Novel compounds of formulae (1) and (2) noted above, which areintermediates in the above-mentioned methods.

In those, X, Y, R¹ and SO₂R² have the same meanings as defined above.

(vi) One embodiment of the method (iv), in which the compound of formula(2) is prepared by reacting a compound of formula (1) noted above with areagent for inserting a sulfonic acid-type leaving group thereinto,preferably by reacting it with a sulfonyl halide or a sulfonic acidanhydride, or reacting it with sulfuryl chloride and then with an amineor a halogens such as a fluorine or the like.

(vii) One embodiment of the method (i) or (ii), which comprises at leastone of the following steps (A) to (E):

(A): a step of forming a compound of formula (3) according to the step(a) or (b) in the method (iv) noted above,

(B): a step of dehalogenating a compound represented by the followinggeneral formula (7) to give a compound represented by the followinggeneral formula (4),

(C): a step of reacting a compound represented by the following generalformula (6) with a reagent for selectively protecting the 5′-position ofthe compound to give a compound of formula (1) noted above,

(D): a step of subjecting a compound of formula (1) noted above toreaction of inserting a sulfonic acid-type leaving group thereinto,preferably by reacting the compound with a sulfonyl halide or a sulfonicacid anhydride, or reacting it with sulfuryl chloride and then with anamine or a halogen such as a fluorine or the like, to give a compound ofthe following general formula (2), and

(E): a step of selectively halogenating a compound of the followinggeneral formula (4) at its 6-position with a halogenating agent to givea compound represented by the following general formula (5).

In those above formulae, as so mentioned hereinabove, X represents ahalogen atom, Y represents a substituent of any one of a fluorine atom,an azido group and a cyano group, R¹ represents a protective group forthe hydroxyl group, SO₂R² represents a sulfonic acid-type leaving group,in which R² is preferably a substituent of any of a halogen atom, and anaryl, alkyl or aralkyl group which may be optionally substituted (forexample, with a halogen atom, etc.), and an alkylamino group which maybe optionally substituted (for example, with a halogen atom, etc.), andR³ represents a protective group for the hydroxyl group.

(viii) Novel compounds of formula (4) noted above, which areintermediates in the above-mentioned methods.

As so mentioned hereinabove, R³ represents a protective group for thehydroxyl group.

(ix) A method for producing intermediates, which comprises at least anyone of the steps (B) to (E).

This method for producing intermediates is usable in the method (vii)noted above. Apart from this, the method is also applicable to theproduction of other various useful compounds, as being simple and easy.Anyhow, this method is an excellent method for producing variousintermediates.

In those formulae, as so mentioned hereinabove, X represents a halogenatom, Y represents a substituent of any one of a fluorine atom, an azidogroup and a cyano group, R¹ represents a protective group for thehydroxyl group, SO₂R² represents a sulfonic acid-type leaving group, inwhich R² is preferably a substituent of any one of a halogen atom, andan aryl, alkyl or aralkyl group which may be optionally substituted (forexample, with a halogen atom, etc.), and also an alkylamino group whichmay be optionally substituted (for example, with a halogen atom, etc.),and R³ represents a protective group for the hydroxyl group.

(x) Another embodiment of the method (i) or (ii) for producingnucleoside derivatives of the above-mentioned compounds (8), (8′) or(9), in which is used any one in the intermediates covered in the (viii)noted above.

In this, as so mentioned hereinabove, X represents a halogen atom, Yrepresents a substituent of any one of a fluorine atom, an azido groupand a cyano group, R¹ represents a protective group for the hydroxylgroup, SO₂R² represents a sulfonic acid-type leaving group such as thatmentioned above, in which R² is preferably a substituent of any one of ahalogen atom, and an aryl, alkyl or aralkyl group which may beoptionally substituted (for example, with a halogen atom, etc.), andalso an alkylamino group which may be optionally substituted (forexample, with a halogen atom, etc.), and R³ represents a protectivegroup for the hydroxyl group.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Modes of carrying out the invention are described below.

Compounds of formula (7) noted above, such as typically9-(2,5-di-O-acetyl-3-bromo-3-deoxy-β-D-xylofuranosyl)adenine, which areused in the invention, can be produced with ease in accordance withknown methods (for example, see J. G. Moffatt, et al., J. Am. Chem.Soc., (95), page 4025, 1973). The substituent W is a halogen atom suchas bromine.

The hydroxyl-protecting group, R³ includes, for example, an acyl group(having from 1 to 10 carbon atoms), such as acetyl or benzoyl; anaralkyl group such as benzyl; and an alkyl group (having from 1 to 5carbon atoms), such as allyl.

Compounds of formula (4) noted above for use in the invention can beobtained by de-halogenating the compounds of formula (7). Tode-halogenate them, employable is any per-se known de-halogenatingmethod, but preferred is a method of reducing the compound (7) with aradical reaction reagent, such as tri-n-butyl tin hydride,tris(trimethylsilyl)silane, diphenylsilane or diphenylmethylsilane inthe presence of a radical reaction initiator such asazobisisobutyronitrile; or a method of reducing it with hydrogen in thepresence of a reduction catalyst such as palladium-carbon or Raneynickel.

The compounds of formula (4) for use in the invention can also beobtained in any per-se known method (for example, a method for producingthem from compounds of formula (7), such as that described by H.Shiragami et al., in Nucleosides & Nucleotides, (15), page 31, 1996).For example, 3′-deoxyinosine is prepared and any hydroxyl groups of thecompound are protected to give the intended compound (4).

Compounds of formula (5) noted above for use in the invention have ahalogen atom (e.g., chlorine) at the 6-position, and these arepreferably obtained by halogenating a compound of formula (4)selectively at its 6-position with a halogenating agent. Thehalogenating agent includes, for example, a chlorinating agent of acombination of phosphorus oxychloride and N,N-dimethylaniline or acombination of sulfuryl chloride and dimethylformamide, and achlorinating agent of dimethylchloromethyleneammonium chloride.

Compounds of formula (6) noted above for use in the invention can beobtained by de-protecting the compounds of formula (5). For thede-protection, preferably used is a mild method that may have noinfluence on the 6-halogen atom of the compounds (5). For example,compounds of formula (5) wherein X is a chlorine atom and R³ is an acylgroup, can be easily de-protected with ammonia or sodium methoxide asdissolved in an alcohol, such as methanol, without being influenced atthe chlorine atom.

Compounds of formulae (5) and (6) noted above for use in the inventionmay be produced in per-se known methods (for example, see C. K. Chu etal., WO-9709052 (1997); Frederick William Hurry et al., Japanese PatentKokoku Publication JP-B-42-17903), or that is, by coupling the nucleicacid base moiety and the saccharide moiety. In general, however, theknown methods produce mixtures with unnecessary α-anomers, and thereforeindispensably require the separation of the intended products from themixtures. In addition, the yield of the intended products to be producedin the known methods is low. Therefore, the method of the invention thatuses compounds (4) is preferred, as being easy and economical inindustrial production of the compounds (5) and (6). The inventionencompasses those compounds (4).

Compounds of formula (1) noted above, which the invention encompasses,can be produced by reacting the compound of formula (6) with a reagentcapable of selectively protecting the 5′-position of the nucleosides.

In formula (1), R¹ is a protective group for the hydroxyl group, whichmay or may not be substituted (for example, with a halogen atom, analkyl group having from 1 to 5 carbon atoms, an alkyloxy group havingfrom 1 to 5 carbon atoms, etc.), and the protective group includes, forexample, an acyl group such as acetyl or benzoyl; an alkyl group such asmethoxymethyl or allyl; an aralkyl group such as benzyl ortriphenylmethyl; a silyl group such as trimethylsilyl. As the reagentthat gives such a protective group, for example, preferably used is anyof an acylating agent, an alkylating agent, an aralkylating agent and anorganic silylating agent. The acylating agent includes, for example,acid anhydrides such as acetic anhydride and benzoic anhydride, and acidhalides such as acyl chloride and benzoyl chloride.

The alkylating agent includes, for example, alkyl halides such aschloromethyl methyl ether and allyl bromide. The aralkylating agentincludes, for example, aralkyl halides such as benzyl bromide andtriphenylmethyl chloride. The organic silylating agent includes, forexample, organic silyl halides such as trimethylsilyl chloride. Thereaction of the compound (6) with the protecting reagent is preferablyeffected in the presence of a base. The base usable in the reactionincludes, for example, hydroxylamine, ammonia and their salts; primaryto quaternary amines and their salts; metal hydroxides such as bariumhydroxide; metal alkoxides such as sodium methoxide and potassiummethoxide; lithium-ammonia solution; ion exchange resins; carbonatessuch as potassium carbonate, sodium carbonate and sodiumhydrogencarbonate; phosphates such as disodium phosphate; acetates suchas sodium acetate; and alkaline solutions of sodium hydroxide, lithiumhydroxide or the like.

Regarding the reaction condition, the two may be reacted in a suitablesolvent. As the solvent, preferably used is an organic solvent such asethyl acetate, toluene, methylene chloride or methanol. The reactionsolvent may be or may not be dewatered. Anyhow, after the reaction, thebase, if used, in the reaction mixture is optionally neutralized, andthe product formed can be isolated from the mixture through ordinaryextraction using an organic solvent such as ethyl acetate, toluene ormethylene chloride. Apart from this, the reaction mixture may bedirectly subjected to the next step without isolating the producttherefrom.

Compounds of formula (1) wherein R³ and R¹ are the same, for example,R³=R¹=acetyl or benzoyl, may be obtained by de-protecting the compoundof formula (5) selectively at the 2′-protective group.

Of compounds of formula (2) noted above, the hydrogen atom in the2′-hydroxyl group is substituted with a sulfonic acid-type leaving group(SO₂R²). In those, R² is preferably a substituent of any one of ahalogen atom, and an aryl (having from 6 to 10 carbon atoms, such asphenyl), alkyl (having from 1 to 5 carbon atoms) or aralkyl (having from7 to 19 carbon atoms, such as benzyl) group, which may or may not besubstituted (for example, with a halogen atom, an alkyl group havingfrom 1 to 5 carbon atoms, a nitro group, an alkyloxy group of which thealkyl moiety has from 1 to 5 carbon atoms, and the like), and also analkylamino group (having from 1 to 6 carbon atoms), which may or may notbe substituted (for example, with a halogen atom, an alkyl group havingfrom 1 to 5 carbon atoms, a nitro group, an alkyloxy group of which thealkyl moiety has from 1 to 5 carbon atoms, and the like). Morepreferably, the protective group is any one of a chlorosulfonyl group, afluorosulfonyl group, an imidazolesulfonyl group, atrifluoromethanesulfonyl group, a methanesulfonyl group, a anarylsulfonyl group such as a paratoluenesulfonyl,paranitrobenzenesulfonyl and benzenesulfonyl group, and the like.

Those compounds of formula (2) can be obtained by reacting the compoundof formula (1) with a sulfonyl halide or a sulfonic acid anhydride, orby reacting it with sulfuryl chloride and then with an amine or ahalogen. The sulfonyl halide includes, for example, arylsulfonyl halidessuch as paratoluenesulfonyl chloride and paranitrobenzenesulfonylchloride; alkylsulfonyl halides such as methanesulfonyl chloride;aralkylsulfonyl halides such as benzylsulfonyl chloride; andhalogenoalkylsulfonyl halides such as trifluoromethanesulfonyl chloride.The sulfonic acid anhydride includes, for example, arylsulfonic acidanhydrides such as paratoluenesulfonic acid anhydride andparanitrobenzenesulfonic acid anhydride; alkylsulfonic acid anhydridessuch as methanesulfonic acid anhydride; aralkylsulfonic acid anhydridessuch as benzylsulfonic acid anhydride; and halogenoalkylsulfonic acidanhydrides such as trifluoromethanesulfonic acid anhydride. The amineincludes, for example, imidazole. The halogen includes, for example,fluorine.

The reaction to give compounds (2) may be effected in a suitablesolvent. For this, preferably used is an organic solvent such as ethylacetate, toluene or methylene chloride. The reaction may be effected inthe presence of a basic catalyst such as pyridine,dimethylaminopyridine, triethylamine or the like. After the reaction,the basic catalyst, if used, in the reaction mixture is optionallyneutralized, and the product formed can be isolated from the mixturethrough ordinary extraction using an organic solvent such as ethylacetate, toluene and methylene chloride, And the like. Apart from this,the reaction mixture may be directly subjected to the next step withoutisolating the product therefrom.

In compounds of formula (3) noted above for use in the invention, Y isany one of a fluorine atom, an azido group and a cyano group. Thosecompounds (3) can be obtained by reacting the compound of formula (2)preferably with an azide, a cyanide or a fluoride. The azide includes,for example, alkali metal azides such as sodium azide and lithium azide;as well as ammonium azide and trimethylsilyl azide. The cyanideincludes, for example, alkali metal cyanides such as sodium cyanide andlithium cyanide. The fluoride includes, for example, hydrogen fluoride;alkali metal fluorides such as lithium fluoride, potassium fluoride andcesium fluoride; alkylammonium fluorides such as tetrabutylammoniumfluoride, pyridinium polyhydrogenfluoride and triethylaminetrihydrofluoride; alkylaminosulfur trifluorides such asdiethylaminosulfur trifluoride and morpholinosulfur trifluoride; andfluoroalkylamines such as Yarovenko reagent and Ishikawa reagent.

The reaction to give compounds (3) may be effected in a suitablesolvent. For this, preferably used is an organic solvent such as ethylacetate, toluene or methylene chloride. The reaction may be effected inthe presence of a basic catalyst such as pyridine, dimethylaminopyridineor triethylamine. After the reaction, the basic catalyst, if used, inthe reaction mixture is optionally neutralized, and the product formedcan be isolated from the mixture through ordinary extraction using anorganic solvent such as ethyl acetate, toluene or methylene chloride.

Compounds of formula (3) noted above for use in the invention, wherein Yis a fluorine atom, can be obtained by reacting the compound of formula(1) with a fluoride. The fluoride for this includes, for example,alkylaminosulfur trifluorides such as diethylaminosulfur trifluoride andmorpholinosulfur trifluoride. This reaction may be effected in asuitable solvent. For this, preferably used is an organic solvent suchas ethyl acetate, toluene and methylene chloride. The reaction may beeffected in the presence of a basic catalyst such as pyridine,dimethylaminopyridine and triethylamine.

Compounds of formula (3) noted above for use in the invention, wherein Xis a chlorine atom and Y is a fluorine atom, may be processed withammonia as dissolved in methanol under pressure to thereby substitute Xwith an amino group, and thereafter the protective group R¹ in theresulting compounds may be de-protected in any suitable manner to giveFddA. However, the usefulness of the compounds illustrated herein is notlimited to this case.

To produce nucleoside derivatives of formula (8) noted above, forexample, the compounds of formula (3) may be subjected to any of thefollowing reaction steps.

To obtain the derivatives (8) wherein Z is an amino group, the compound(3) is processed with ammonia as dissolved in an alcohol such asmethanol under pressure.

To obtain the derivatives (8) wherein Z is a hydroxyl group, thecompound (3) is processed with an aqueous solution of an alkalihydroxide such as sodium hydroxide and potassium hydroxide.

To obtain the derivatives (8) wherein Z is a hydrogen atom, the compound(3) is processed with hydrogen in the presence of a reduction catalystsuch as palladium-carbon.

To obtain the derivatives (8) wherein Z is an azido group, the compound(3) is processed with an alkali metal azide, such as sodium azide orlithium azide, in a solvent capable of dissolving the metal azide, suchas dimethylformamide.

To obtain the derivatives (8) wherein Z is OR⁴ or SR⁴, the compound (3)is processed with a corresponding alkyl alcohol or alkyl thiol havingbeen activated with an alkali metal halide such as a sodium halide.

To obtain the derivatives (8) wherein Z is NHR⁴, the compound (3) isprocessed with an alkylamine (corresponding to the intended substituent,such as methylamine), preferably in an inert solvent such asdimethylformamide.

In formula (8), R⁴ indicates an optionally phenyl-substituted lower(C1-5) alkyl group, such as a methyl, ethyl, propyl, butyl and benzylgroup.

Nucleoside derivatives of formula (9) may be produced with ease byde-protecting the compounds of formula (8). For example, compounds (8)wherein R¹ is an acyl group such as an acetyl and benzoyl group may beprocessed with an alkali (e.g., sodium hydroxide, potassium hydroxide);those wherein R¹ is an alkyl group such as a methoxymethyl and allylgroup may be processed with an acid such as hydrochloric acid and aceticacid; those wherein R¹ is an aralkyl group such as a benzyl ortriphenylmethyl group may be processed with hydrogen in the presence ofa reduction catalyst such as palladium-carbon and Raney nickel, or maybe processed with an acid such as acetic acid; and those wherein R¹ is asilyl group such as a trimethylsilyl group may be processed withtetraammonium fluoride or the like, to thereby give the derivatives offormula (9).

Alternatively, the above mentioned de-protecting reaction step at the5′-potion thereof may be conducted and then substitution reaction with Zgroup may be conducted. In this case,the compound (3) firstly may besubjected to such above deprotecting step at the protective group R¹ inthe same manner as above to give the derivative (8′), and then thusobtained derivative (8′) may be subjected to substitution with a group Zat its 6-halogen atom to give the compound (9) also in the same manneras above.

EXAMPLES

Now, the invention is described in detail with reference to thefollowing Examples.

Example 1 Production of9-(2,5-di-O-acetyl-3-bromo-3-deoxy-β-D-xylofuranosyl)-1,9-dihydro-6H-purine-6-one

400 g (1.49 mols) of inosine was suspended in 800 ml of acetic acid in a2-liter glass reactor, to which was added 240 ml (1.92 mols) oftrimethyl ortho-acetate, and reacted at 35° C. for 5 hours. The reactionmixture was concentrated under reduced pressure while acetic acid wasadded thereto, to thereby remove almost all methanol therefrom. Theresulting concentrate was dissolved in 900 ml of acetonitrile addedthereto, and cooled at 0° C., to which was dropwise and slowly added 280ml (3.79 mols) of acetyl bromide over a period of about 5 hours. Theresulting white slurry was dropwise added to 1.6 liters of a 1/1 mixtureof water and acetonitrile that had been prepared separately, while beingneutralized with an aqueous solution of 25% sodium hydroxide, wherebythe reaction was stopped. The neutralizing rate was so adjusted that thepH value of the system might fall between 6.0 and 7.0 or so. For thisneutralization, used was about 1.3 liters of the aqueous solution of 25%sodium hydroxide. To the resulting reaction mixture, added was 800 ml ofacetonitrile to separate the organic layer and the aqueous layer. Theaqueous layer was back-extracted with acetonitrile and ethyl acetate.The organic layers were combined and concentrated to have a desiredvolume, and then washed with a saturated saline solution and an aqueoussaturated solution of sodium hydrogencarbonate, dried with anhydrousmagnesium sulfate, and filtered. The solvent was evaporated out from theresulting filtrate, and a syrupy product was obtained. This was analyzedthrough liquid chromatography. The yield of the entitled compound was53.8%.

¹H-NMR (300 MHz, CDCl₃) δ: 8.34 (1H, s, H2), 8.24 (1H, s, H8), 6.20 (1H,bs, H1′) 5.74 (1H, bs, H2′), 4.4 to 4.6 (4H, m, H3′, H4′, H5′ab), 2.20(3H, s, 5′OAc), 2.14 (3H, s, 2′OAc).

IR (KBr, cm⁻¹): 1750, 1698, 1376, 1226, 1043.

UV (MeOH) λmax: 206 (log ε 2.22), 245 (log ε 1.53) nm.

MS (ESI) m/z: 415, 417 (M+H)⁺, 829, 831, 833 (2M+H)⁺.

Example 2 Production of 2′,5′-di-O-acetyl-3′-deoxyinosine

3.67 g (8.85 mmols) of9-(2,5-di-O-acetyl-3-bromo-3-deoxy-β-D-xylofuranosyl)-1,9-dihydro-6H-purine-6-onewas dissolved in 66 ml of toluene in a 200-ml reactor, to which wereadded 7.35 ml (26.5 mmols) of tributyl tin hydride and 125 mg (0.761mmols) of 2,2′-azobisisobutyronitrile. The reaction mixture was heatedup to 95° C. and reacted for 1 hour, and then cooled to 0° C., and thendropwise added to 35 ml of petroleum ether that had been preparedseparately, to stop the reaction. The white precipitate thus formed wastaken out through filtration, and recrystallized from 46 ml of ethanoland 35 ml of acetonitrile hydrate. The crystals were taken out throughfiltration and dried at 40° C. under reduced pressure to obtain 1.88 g(5.58 mmols, yield: 63.1%) of white crystals.

¹H-NMR (300 MHz, CDCl₃) δ: 8.08 (1H, s, H2), 8.07 (1H, s, H2), 6.04 (1H,d, J=1.1 Hz, H1′), 5.59 (1H, bd, J=5.9 Hz, H2′), 4.60 (1H, m, H4′), 4.39(1H, dd, J=12.3, 2.9 Hz, H5′a), 4.22 (1H, dd, J=12.3, 5.2 Hz, H5′b),2.50 (1H, ddd, J=14.0, 10.5, 5.9 Hz, H3′a), 2.16 (1H, ddd, J=14.0, 5.8,1.1 Hz, H3′b), 2.09 (3H, s, 5′OAc), 2.04 (3H, s, 2′OAc).

¹H-NMR (300 MHz, DMSO-d6) δ: 8.26 (1H, s, H2), 8.10 (1H, s H8), 6.11(1H, d, J=1.4 Hz, H1′), 5.61 (1H, bd, J=6.3 Hz, H2′), 4.52 (1H, m, H4′),4.29 (1H, dd, J=12.0, 2.9 Hz, H5′a), 4.16 (1H, dd, J=12.0, 5.8 Hz,H5′b), 2.60 (1H, ddd, J=14.1, 10.3, 6.3 Hz, H3′a), 2.22 (1H, ddd,J=14.1, 5.9, 1.1 Hz, H3′b), 2.10 (3H, s, 5′OAc), 1.99 (3H, s, 2′OAc).

IR (KBr, cm⁻¹): 1746, 1724, 1707, 1419, 1344, 1230, 1205, 1122, 1100.

UV (MeOH) λmax: 203 (log ε 1.42), 245 (log ε 0.83) nm.

MS (ESI) m/z: 359 (M+Na)⁺, 695 (2M+Na)⁺.

Example 3 Production of6-chloro-9-(2,5-di-O-acetyl-3-deoxy-β-D-erythro-pentofuranosyl)-9H-purine

32.7 g (97.2 mmols) of 2′,5′-di-O-acetyl-3′-deoxyinosine was suspendedin 449 ml of methylene chloride in a 1-liter reactor, to which wereadded 30.1 ml (389 mmols) of dimethylformamide and 28.0 ml (389 mmols)of thionyl chloride, and reacted for about 7 hours while heating underreflux. The reaction mixture was cooled to 0° C., and then dropwiseadded to 500 ml of water that had been cooled at 0° C. to stop thereaction. The reaction mixture was separated into layers, and theorganic layer was taken out, and washed with water, an aqueous saturatedsolution of sodium hydrogencarbonate and a saturated saline solution inthat order. The solvent was evaporated, and 31.0 g of an oily productwas obtained. This crude product was directly subjected to the nextreaction.

Example 4 Production of6-chloro-9-(3-deoxy-β-D-erythro-pentofuranosyl)-9H-purine

31.0 g (83.4 mmols) of6-chloro-9-(2,5-di-O-acetyl-3-deoxy-β-D-erythro-pentofuranosyl)-9H-purinewas dissolved in 103 ml of methanol in a 500-ml reactor, and cooled to0° C., to which was added 1.60 g (8.31 mmols) of 28% sodium methoxide.These were reacted at room temperature for 3 hours, and then cooled to0° C. The crystals thus formed were taken out through filtration. Thesewere washed with 18 ml of cold methanol, and then dried at 50° C. underreduced pressure to obtain 14.7 g of white crystals (purity 99.2%; 53.9mmols; overall yield 55.4% [2 stages]).

¹H-NMR (300 MHz, CDCl₃) δ: 8.68 (1H, s, H2), 8.33 (1H, s, H8), 5.83 (1H,d, J=4.6 Hz, H1′), 4.92 (1H, ddd, J=7.2, 6.5, 4.6 Hz, H2′), 4.56 (1H, m,H4′), 3.98 (1H, dd, J=12.5, 2.1 Hz, H5′a), 3.60 (1H, dd, d=12.5, 2.6 Hz,H5′b), 2.53 (1H, ddd, J=12.9, 7.2, 5.7 Hz, H3′a), 2.18 (1H, ddd, J=12.9,8.0, 6.5 Hz, H3′b).

¹H-NMR (300 MHz, DMSO-d6) δ: 8.97 (1H, s, H2), 8.82 (1H, s, H8), 6.06(1H, d, J=1.4 Hz, H1′), 5.80 (1H, s, J=3.9 Hz, H2′—OH), 5.12 (1H, dd,J=5.3, 5.2 Hz, H5′—OH), 4.65 (1H, m, H2′), 4.46 (1H, m, H4′), 3.78 (1H,ddd, J=12.1, 5.3, 3.2 Hz, H5′a), 3.59 (1H, ddd, J=12.1, 5.2, 3.8 Hz,H5′b), 2.28 (1H, ddd, J=13.3, 9.6, 5.3 Hz, H3′a), 1.93 (1H, ddd, J=12.3,6.0, 2.2 Hz, H3′b).

IR (KBr, cm⁻¹): 3331, 3105, 3074, 2938, 2920, 1596, 1562, 1492, 1442,1426, 1405, 1391, 1337, 1207, 1129, 1079, 1068, 1002, 979, 834, 806,635.

UV (MeOH) λmax: 204 (log ε 1.17), 265 (log ε 0.45) nm.

MS (ESI) m/z: 271 (M+H)⁺.

Example 5 Production of6-chloro-9-[3-deoxy-5-O-(triphenylmethyl)-β-D-erythro-pentofuranosyl]-9H-purine

1.38 g (5.10 mmols) of6-chloro-9-(3-deoxy-β-D-erythro-pentofuranosyl)-9H-purine was dissolvedin 41 ml of dry dimethylformamide, to which were added 2.3 ml (16.5mmols) of triethylamine and 0.424 g (3.47 mmols) of4-dimethylaminopyridine. Then, 4.79 g (16.8 mmols) of trityl chloridewas added thereto, and these were reacted for about 16.5 hours at 50° C.After having been cooled, 8 ml of water was added to the reactionmixture, and the solvent was evaporated therefrom. The removal of thesolvent was repeated four times. The residue was dissolved in 100 ml ofmethylene chloride and 50 ml of water. After having been thus separated,the organic layer was washed four times with 50 ml of water each, driedwith anhydrous sodium sulfate, and then filtered. The resulting filtratewas applied to a silica gel column (silica: 100 g), and eluted withmethylene chloride and then with 1 to 10% methanol/methylene chloridesolutions. The solvent was evaporated to obtain 2.71 g of an oilyproduct (purity 85.3%; yield 88.5%).

¹H-NMR (300 MHz, CDCl₃) δ: 8.64 (1H, s, H2), 8.40 (1H, s H8), 7.41 to7.21 (15H, m, 5′OTr), 6.04 (1H, d, J=2.2 Hz, H1′), 4.87 (1H, m, H2′),4.73 (1H, m, H4′), 3.44 (1H, dd, J=10.6, 3.1 Hz, H5′a), 3.33 (1H, dd,J=10.6, 4.6 Hz, H5′b), 2.30 (1H, ddd, J=13,3. 7.7, 5.6 Hz, H3′a), 2.17(1H, ddd, J=13.3, 6.5, 3.9 Hz, H3′b).

IR (KBr, cm⁻¹): 3354, 3059, 1592, 1562, 1491, 1449, 1400, 1338, 1206,1130, 1078, 1018, 952, 766, 748, 704, 634.

UV (MeOH) λmax: 207 (log ε 2.27), 265 (log ε 0.31) nm.

MS (ESI) m/z: 513 (M+H)⁺.

Example 6 Production of6-chloro-9-[2,3-dideoxy-2-fluoro-5-O-(triphenylmethyl)-β-D-threo-pentofuranosyl]-9H-purine,Part 1

104 mg (0.202 mmols) of6-chloro-9-[3-deoxy-5-O-(triphenylmethyl)-β-D-erythro-pentofuranosyl]-9H-purine,purine was dissolved in 10 ml of methylene chloride in a 30-ml reactor,to which was added 0.12 ml (1.48 mmols) of pyridine. This mixture wascooled to 0° C., to which was dropwise added 0.07 ml (0.530 mmols) ofdiethylaminosulfur trifluoride with stirring. Next, this was restored tobe at room temperature, and then heated under reflux or about 4 hours.After having been again restored to be at room temperature, this wasdropped into a mixture of 20 ml of an aqueous saturated solution ofsodium hydrogencarbonate and 10 ml of methylene chloride with vigorouslystirring, and then further stirred for about 20 minutes. The reactionmixture was separated into layers, and the organic layer wasconcentrated azeotropically with toluene. The residue was taken out andpurified through a silica gel plate (using 50% hexane/ethyl acetate).The fraction of the intended product was extracted with ethyl acetate,and the solvent was evaporated to obtain 44.3 mg (yield 42.6%) of theobjective compound, which was white solid.

¹H-NMR (300 MHz, CDCl₃) δ: 8.73 (1H, s, H2), 8.34 (1H, d, J=2.8 Hz, H8),7.52 to 7.22 (15H, m, 5′OTr), 6.41 (1H, dd, J=19.1, 3.1 Hz, H1′), 5.25(1H, dddd, J=53.7, 5.2, 3.1, 2.0 Hz, H2′), 4.46 (1H, m, H4′), 3.48 (1H,dd, J=9.9, 6.6 Hz, H5′a), 3.30 (1H, dd, J=9.9, 3.8 Hz, H5′b), 2.57 (1H,dddd, H=35.0, 14.8, 9.0, 5.6 Hz, H3′a), 2.36 (1H, dddd, J=27.5, 15.1,5.1, 1.7 Hz, H3′b).

IR (KBr, cm⁻¹): 1593, 1567, 1492, 1220, 1206, 1079, 708.

UV (MeOH) λmax: 204 (log ε 1.17), 265 (log ε 0.45) nm.

MS (ESI) m/z: 515 (M+H)⁺.

Example 7 Production of6-chloro-9-[2-O-(sulfurylimidazolyl)-3-deoxy-5-O-(triphenylmethyl)-β-D-erythro-pentofuranosyl]-9H-purine

604 mg (1.18 mmols) of6-chloro-9-[3-deoxy-5-O-(triphenylmethyl)-β-D-erythro-pentofuranosyl]-9H-purinewas dissolved in 11.8 ml of methylene chloride, to which was added 486mg (7.07 mmols) of imidazole. This reaction mixture was cooled to −35°C., to which was added 0.15 ml (1.77 mmols) of sulfuryl chloride, andstirred for 30 minutes. Then, after having been restored to be at roomtemperature, this was stirred overnight. To the reaction mixture, waterwas added to stop the reaction. Then, the mixture was separated intolayers, and the aqueous layer was washed with dichloromethane. Theorganic layers were combined together, dried with anhydrous sodiumsulfate, and filtered. The solvent was evaporated from the resultingfiltrate. The residue was purified through silica gel column (silica 40g), using 33 to 50% hexane/ethyl acetate, to obtain 570 mg (yield 75.0%)of the intended product, which was colorless oil.

¹H-NMR (300 MHz, CDCl₃) δ: 8.67 (1H, s, H2), 8.25 (1H, s, H8), 8.03 (1H,s, imidazole), 7.37 to 7.24 (16H, m, 5′OTr+imidazole), 7.16 (1H, s,imidazole), 6.11 (1H, s, H1′), 5.93 (1H, d, J=5.3 Hz, H2′), 4.65 (1H, m,H4′), 3.46 (1H, dd, J=10.8, 3.2 Hz, H5′a), 3.35 (1H, dd, J=10.8, 4.5 Hz,H5′b), 2.61 (1H, ddd, J=14.6, 9.7, 5.3 Hz, H3′a), 2.27 (1H, ddd, J=14.6,5.7, 1.6 Hz, H3′b).

Example 8 Production of6-chloro-9-[2,3-dideoxy-2-fluoro-5-O-(triphenylmethyl)-β-D-threo-pentofuranosyl]-9H-purine,Part 2

113 mg (0.176 mmols) of6-chloro-9-[2-O-(sulfurylimidazolyl)-3-deoxy-5-O-(triphenylmethyl)-β-D-erythro-pentofuranosyl]-9H-purinewas dissolved in 1.80 ml of toluene, to which was added 0.18 ml (1.06mmols) of triethylamine trihydrofluoride, and stirred overnight at 50°C. After having been cooled, 10.0 ml of ethyl acetate and 8.0 ml of anaqueous saturated solution of sodium hydrogencarbonate were added tothis, to separate it into layers. The organic layer was dried withanhydrous sodium sulfate, and filtered. Then, the solvent was evaporatedfrom the filtrate. The residue was dissolved in acetonitrile andanalyzed through liquid chromatography. The intended product wasobtained at an yield of 41.9%.

Example 9 Production of6-chloro-9-[2-O-(trifluoromethanesulfonyl)-3-deoxy-5-O-(triphenylmethyl)-β-D-erythro-pentofuranosyl]-9H-purine

164 mg (0.320 mmols) of6-chloro-9-[3-deoxy-5-O-(triphenylmethyl)-β-D-erythro-pentofuranosyl]-9H-purinewas dissolved in 9 ml of methylene chloride, to which was added 253 mg(3.20 mmols) of pyridine. To this mixture, dropwise added was a mixtureof 361 ml of trifluoromethanesulfonic acid anhydride and 2 ml ofmethylene chloride at room temperature, and the resulting mixture wasthen stirred at room temperature for about 15 minutes. To the reactionmixture was added a mixture of 20 ml of an aqueous saturated solution ofammonium chloride and 10 ml of methylene chloride, by which the reactionwas stopped. The organic layer separated was taken out, and then washedwith an aqueous saturated solution of ammonium chloride, an aqueoussaturated solution of sodium hydrogencarbonate and a saturated saline inthat order. Then, the thus-washed organic layer was dried with anhydrousmagnesium sulfate, and filtered. The solvent was evaporated out from thefiltrate to obtain a white foamy solid. Analyzing this throughhigh-performance liquid chromatography (HPLC) verified that the solidobtained was nearly a single substance. This solid was directlysubjected to the next reaction step.

Example 10 Production of6-chloro-9-[2,3-dideoxy-2-fluoro-5-O-(triphenylmethyl)-β-D-threo-pentofuranosyl]-9H-purine,Part 3

22.9 mg (0.0356 mmols) of6-chloro-9-[2-O-(trifluoromethanesulfonyl)-3-deoxy-5-O-(triphenylmethyl)-β-D-erythro-pentofuranosyl]-9H-purinewas dissolved in 2.0 ml of toluene, to which were added 10.8 mg (0.107mmols) of triethylamine and 34.5 mg (0.214 mmols) of triethylaminetrihydrofluoride, and stirred at room temperature for about 5 days.After having been cooled, all the mixture was dissolved in methanol, andanalyzed through liquid chromatography. The intended product wasobtained at an yield of 57.8%.

Example 11 Production of9-[2,3-dideoxy-2-fluoro-5-O-(triphenylmethyl)-β-D-threo-pentofuranosyl]-9H-purine-6-amine

110 mg (0.214 mmols) of6-chloro-9-[2,3-dideoxy-2-fluoro-5-O-(triphenylmethyl)-β-D-threo-pentofuranosyl]-9H-purinewas dissolved in 17.2 ml of a solution of 20% ammonia/methanol, and keptovernight in a closed vessel at 60° C. After having been cooled, thereaction mixture was concentrated, and then distilled azeotropicallywith toluene. The crystals formed were taken out through filtration.These were dried at room temperature under reduced pressure to obtain82.3 mg of a white solid (purity 74.4%; yield 57.7%).

¹H-NMR (300 MHz, CDCl₃) δ: 8.33 (1H, s, H2), 8.06 (1H, d, J=3.0 Hz, H8),7.52 to 7.20 (15H, m, 5′OTr), 6.33 (1H, dd, J=19.9, 2.9 Hz, H1′), 6.18(2H, bs, 6-NH2), 5.20 (1H, md, J=53.8 Hz, H2′), 4.40 (1H, m, H4′), 3.46(1H, dd, J=10.0, 6.5 Hz, H5′a), 3.27 (1H, dd, J=10.0, 4.1 Hz, H5′b),2.50 (1H, dddd, J=35.5, 14.9, 9.0, 5.4 Hz, H3′a), 2.31 (1H, dddd,J=27.5, 14.9, 4.8, 1.4 Hz, H3′b).

IR (KBr, cm⁻¹): 3151, 1649, 1599, 1578, 1403, 1063, 703

UV (MeOH) λmax: 208 (log ε 2.19), 259 (log ε 0.58) nm.

MS (ESI) m/z: 496 (M+H)⁺.

Example 12 Production of 9-(2,3-dideoxy-2-fluoro-β-D-threo-pentofuranosyl)-9H-purine-6-amine

35.3 mg (0.0710 mmols) of9-[2,3-dideoxy-2-fluoro-5-O-(triphenylmethyl)-β-D-threo-pentofuranosyl]-9H-purine-6-aminewas dissolved in 1.0 ml of acetic acid, and stirred at room temperaturefor about 4 hours and then at 80° C. for about 3 hours. To this wasadded 1.0 ml of acetic acid, and cooled to room temperature. This wasconcentrated, and the residue formed was taken out and purified througha silica gel plate (using 91% methylene chloride/ethanol). The fractionof the intended product was extracted with methanol, and the solvent wasevaporated out to obtain 11.1 mg (yield 61.5%) of the product which waswhite solid. The physical data of the product obtained herein were thesame as those disclosed in the literature.

Example 13 Production of6-chloro-9-[2-azido-2,3-dideoxy-5-O-(triphenylmethyl)-β-D-threo-pentofuranosyl]-9H-purine

1.0 g (1.95 mmols) of6-chloro-9-[3-deoxy-5-O-(triphenylmethyl)-β-D-erythro-pentofuranosyl]-9H-purinewas dissolved in 20 ml of methylene chloride. This mixture was cooled to0° C., to which was added 0.47 ml (5.85 mmols) of pyridine. To thismixture, dropwise was added 0.66 ml (3.90 mmols) oftrifluoromethanesulfonic acid anhydride, and the resulting mixture wasthen stirred at room temperature for about 1 hour. To the reactionmixture was added a mixture of 20 ml of an aqueous saturated solution ofsodium hydrogencarbonate and 20 ml of methylene chloride, by which thereaction was stopped. The organic layer thus separated was taken out,and then washed with water. Then, the thus-washed organic layer wasdried with anhydrous sodium sulfate, and filtered. The solvent wasevaporated out from the filtrate to obtain an oily material. This oilymaterial was dissolved in 10 ml of toluene and the solvent. wasevaporated out from the mixture to obtain a white foamy solid. Thissolid was directly subjected to the next step.

1.473 g of this solid was dissolved in 20 ml of dry dimethylformamide.This mixture was cooled to 0° C., to which was added 126.8 mg (1.95mmols) of sodium azide, and stirred at room temperature for 1.5 hours.To the reaction mixture was added a mixture of 100 ml of methylenechloride and 70 ml of water having two phases, by which the reaction wasstopped. The organic layer and the aqueous layer were separated. Theaqueous layer was back extracted with a mixture of 100 ml of ethylacetate and 100 ml of a saturated saline. The organic layers werecombined together, dried with anhydrous sodium sulfate and filtered. Thesolvent was evaporated from the resulting filtrate. The residue waspurified through silica gel column (silica gel 80 g), using 30 to 80%ethyl acetate/hexane, to obtain 0.84 g (yield 80%) of the intendedproduct.

1H-NMR(300 MHz,CDCl3) δ: 8.72 (s,1H,H8), 8.37 (s,1,H2),7.20-7.54(m,15H,Tr),6.43 (d,J=5.4 Hz,1H,H1′),4.54 (m,1H,H2′),4.40 (m,1H,H4′),3.50(dd,J=10.4,5.5 Hz,1H,H5′a),3.41 (dd,J=10.4,4.0 Hz,1H,H5′b),2.20-2.59(m,2H,H3′).

MS(ESI)m/z:538 (M+H)⁺.

Example 14 Production of9-(2,3-dideoxy-2-fluoro-β-D-threo-pentofuranosyl)-9H-purine-6-amine(FddA), Part 2

3.65 g (7.09 mmols) of6-chloro-9-[2,3-dideoxy-2-fluoro-5-O-(tripenylmethyl-β-D-threo-pentofuranosyl]-9H-purinewas dissolved in 18 ml of methanol and 18 ml of toluene which iscontaining 0.5 equivalent of hydrogen chloride. This mixture was stirredat room temperature for about 4 hours. This was treated with 2equivalents of poly (4-vinylpyridine), and filtered. The solvent wasevaporated out from the filtrate under the reduced pressure. The residuewas dissolved in 200 ml of methanol and 200 ml of toluene.

The mixture was kept under 3.5 bar of ammonia pressure in a closedvessel at 40 to 60° C. for 5 days. After having been cooled, thereaction mixture was concentrated, and added 80% acetone water solution.The crystals thus formed were taken out through filtration. These weredried and analyzed through liquid chromatography. The intended product,FddA, was obtained at an yield of 73% in two steps.

Effects of the Invention

According to the present invention, substrates of which the 3′-positionof the saccharide moiety is deoxylated can be substituted at the2′-position at a high yield to give nucleoside derivatives. Therefore,using the method of the invention, nucleoside derivatives including9-(2,3-dideoxy-2-fluoro-β-D-threo-pentofuranosyl)adenine (FddA) andtheir related compounds can be produced in a simplified manner at a highyield. Accordingly, the method of the invention gives those nucleosidederivatives at low costs.

What is claimed is:
 1. A method for producing a nucleoside derivative represented by formula (8) or (9):

wherein Y represents a fluorine atom, an azido group or a cyano group; Z represents a hydrogen atom, an amino group, a hydroxyl group, an azido group, a substituent represented by formula OR⁴, a substituent represented by formula SR⁴ or a substituent represented by formula NHR⁴; R¹ represents hydroxyl protecting group; and R⁴ represents a lower alkyl group which is optionally substituted with one or more phenyl groups, comprising: reacting a 3′-deoxy derivative of inosine represented by formula (4), wherein R³ represents a protective group for the hydroxyl group, with a halogenating agent to produce the corresponding 6-halo derivative of inosine represented by formula (5),

removing the 2′ protecting group and the 5′-protecting group from the compound of formula (5) to produce the compound of formula (6):

and selectively protecting the 5′-hydroxyl of the compound of formula (6) with an R^(1,)group wherein R¹ represents a hydroxyl protecting group and X represents a halogen atom, to produce the compound of formula (1), converting the 2′-hydroxyl group of the 6-halo derivative of inosine represented by formula (1) to an O-leaving group; displacing the O-leaving group with a nucleophile selected from the group consisting of a fluoride ion, an azide ion and a cyanide ion; and then substituting the halogen atom at the 6-position of the inosine derivative with a substituent selected from the group consisting of a hydrogen atom, an amino group, a hydroxyl group, an azido group, a substituent represented by formula OR⁴, a substituent represented by formula SR⁴ and a substituent represented by formula NHR⁴, wherein R⁴ is as defined above, wherein said 6-halo derivative represented by formula (1) is optionally reacted with diethylaminosulfur trifluoride to produce the corresponding 2′-fluoro derivative, and then subjected to said substituting at the 6-position thereof.
 2. The method of claim 1, wherein said converting the 2′-hydroxyl group of a compound represented by formula (1) to a leaving group produces a compound represented by formula (2):

wherein X represents a halogen atom; R¹ represents a hydroxyl protecting group; O—SO₂R² represents a sulfonic acid-type leaving group.
 3. The method of claim 1, wherein Y is a fluorine atom.
 4. The method of claim 1, wherein Z is an amino group.
 5. The method of claim 1, further comprising: removing the R¹ protecting group from the compound represented by formula (8) to provide a compound represented by formula (9):

wherein Y and Z are as defined in claim
 1. 6. A method of producing a compound represented by formula (4), comprising: dehalogenating a compound represented by formula (7) to provide the compound represented by formula (4);

wherein W represents a halogen atom; and R³ represents a hydroxyl protecting group.
 7. A method of producing the compound represented by formula (1), comprising: producing the compound represented by formula (4) according to claim 6; reacting the compound represented by formula (4) with a halogenating agent to produce the corresponding 6-halo derivative represented by formula (5); and removing the R³ groups of the 6-halo derivative represented by formula (5) to produce the compound represented by formula (6); and selectively protecting the 5′ hydroxyl group of the compound represented by formula (6) with a R¹ group,

wherein R¹ represents a hydroxyl protecting group; R³ represents a hydroxyl protecting group; and X represents a halogen atom.
 8. A method of producing a compound represented by formula (3): wherein

X represents a halogen atom; Y represents a fluorine atom; and R¹ represents a hydroxyl protecting group, comprising: converting the 2′-hydroxyl group of a compound represented by formula (1) to an O-leaving group: and displacing the O-leaving group with a fluoride ion to produce the compound

 represented by formula (3); or reacting a compound represented by formula (1) with diethylaminosulfur trifluoride to produce a compound represented by formula (3).
 9. A method of producing a compound represented by formula (8′):

wherein X represents a halogen atom; and Y represents a fluorine atom, an azido group or a cyano group; comprising: producing the compound represented by formula (3) according to claim 8; and removing the R¹ protecting group from the compound represented by formula (3), to produce the compound represented by formula (8′).
 10. A method of producing a compound represented by formula (9):

wherein Y represents a fluorine atom, an azido group or a cyano group; and Z represents a hydrogen atom, an amino group, a hydroxyl group, an azido group, a substituent represented by formula OR⁴, a substituent represented by formula SR⁴ or a substituent represented by formula NHR⁴; and R⁴ represents a lower alkyl group which is optionally substituted with one or more phenyl groups, further comprising: producing the compound represented by formula (3) according to claim 8; and substituting the halogen atom at the 6-position of the compound of formula (3) with a substituent selected from the group consisting of a hydrogen atom, an amino group, a hydroxyl group, an azido group, a substituent represented by formula NHR⁴, a substituent represented by formula OR⁴, and a substituent represented by formula SR⁴ to produce the compound represented by formula (8), or removing the protecting group R¹ from the compound of formula (3), to provide the compound represented by formula (8′),

wherein X represents a halogen atom; Y represents a fluorine atom, an azido group or a cyano group; Z represents a hydrogen atom, an amino group, a hydroxyl group, an azido group, a substituent represented by formula OR⁴, a substituent represented by formula SR⁴ or a substituent represented by formula NHR⁴; and substituting the halogen atom at the 6-position of the compound of formula (8′) with a substituent selected from the group consisting of a hydrogen atom, an amino group, a hydroxyl group, an azido group, a substituent represented by formula OR⁴, a substituent represented by formula SR⁴ and a substituent represented by formula NHR⁴; or removing the R¹ protecting group from the compound of formula (8) to produce the compound represented by formula (9).
 11. A method of producing a compound represented by formula (3):

wherein X represents a halogen atom; Y represents a fluorine atom, an azido group or a cyano group; and R¹ represents a hydroxyl protecting group, comprising: converting the 2′ hydroxyl group of a compound represented by formula (1) to an O-leaving group:

and displacing the O-leaving group with a fluoride, azide or cyanide ion to produce the compound represented by formula (3).
 12. A method of producing a compound represented by formula (8′):

wherein X represents a halogen atom; and Y represents a fluorine atom, an azido group or a cyano group; comprising: producing the compound represented by formula (3) according to the method of claim 11; and removing the R¹ group, to produce the compound represented by formula (8′).
 13. A method of producing a compound represented by formula (9):

wherein Y represents a fluorine atom, an azido group or a cyano group; and Z represents a hydrogen atom, an amino group, a hydroxyl group, an azido group, a substituent represented by formula OR⁴, a substituent represented by formula SR⁴ or a substituent represented by formula NHR⁴; and R⁴ represents a lower alkyl group which is optionally substituted with one or more phenyl groups comprising: producing the compound represented by formula (8′) according to the method of claim 12; and substituting the halogen atom at the 6 position with a substituent selected from the group consisting of a hydrogen atom, an amino group, a hydroxyl group, an azido group, a substituent represented by formula OR⁴, a substituent represented by formula SR⁴ and a substituent represented by formula NHR⁴, wherein R⁴ is defined above, to produce the compound represented by formula (9). 